Math 函数
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hypot

(PHP 4 >= 4.1.0, PHP 5)

hypot — 计算一直角三角形的斜边长度

说明

float hypot ( float $x , float $y )

hypot() 函数将会跟据直角三角形的两直解边长度 x 和 y 计算其斜边的长度。或者是从标点 (x, y) 到原点的距离。该函数的算法等同于 sqrt(x*x + y*y)。

Math 函数
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PHP手册
PHP手册 - N: 计算一直角三角形的斜边长度

用户评论:

</Life>.org (10-Aug-2006 10:56)

to robinv at ecosse dot net:

hypo(a, b, c) === hypo(a, hypo(b, c))
hypo(a, b, c, d) === hypo(a, hypo(b, hypo(c, d)))
...

R. Victor Klassen (24-Jun-2005 04:03)

A correct implementation of hypot( x, y ) avoids the overflow that might otherwise happen if either x or y is large enough that when squared it would overflow, but the answer is small enough not to cause overflow.

robinv at ecosse dot net (07-Jan-2004 05:18)

A simpler approach would be to allow an arbitrary number of parameters. That would allow for whatever number of dimensions you want *and* it would be backwards compatible with the current implementation.

<?php

function hypo()
{
    $sum = 0;
    foreach (func_get_args() as $dimension) {
        if (!is_numeric($dimension)) return -1;
        $sum += pow($dimension, 2);
    }
    return sqrt($sum);
}

print hypo();          // vector in 0 dimensions, magnitude = 0.
print hypo(1);         // vector in 1 dimension,  magnitude = 1.
print hypo(3, 4);       // vector in 2 dimensions, magnitude = 5.
print hypo(2, 3, 6);     // vector in 3 dimensions, magnitude = 7.

?>